6,034 research outputs found
Recommended from our members
Palaeolimnology of Lake Sapanca and identification of historic earthquake signals, Northern Anatolian Fault Zone (Turkey)
Lake Sapanca is located on a strand of the Northern Anatolian Fault Zone (NAFZ, Turkey), where a series of strong earthquakes (Ms >6.0) have occurred over the past hundred years. Identifying prehistoric
earthquakes in and around Lake Sapanca is key to a better understanding of plate movements along the
NAFZ. This study contributes to the development of palaeolimnological tools to identify past earthquakes
in Lake Sapanca. To this end several promising proxies were investigated, specifically lithology, magnetic
susceptibility, grain size (thin-section and laser analysis), geochemistry, pollen concentration, diatom
assemblages, 137Cs and 210Pb. Sedimentological indicators provided evidence for reworked, turbidite-like
or homogeneous facies (event layers) in several short cores (<45 cm). Other indicators of sediment input
and the historical chronicles available for the area suggest that three of these event layers likely originated
from the AD 1957, 1967 and 1999 earthquakes. Recent changes in sediment deposition and nutrient
levels have also been identified, but are probably not related to earthquakes. This study demonstrates
that a combination of indicators can be used to recognize earthquake-related event layers in cores that encompass a longer period of time
Anisotropic conductivity of disordered 2DEGs due to spin-orbit interactions
We show that the conductivity tensor of a disordered two-dimensional electron
gas becomes anisotropic in the presence of both Rashba and Dresselhaus
spin-orbit interactions (SOI). This anisotropy is a mesoscopic effect and
vanishes with vanishing charge dephasing time. Using a diagrammatic approach
including zero, one, and two-loop diagrams, we show that a consistent
calculation needs to go beyond a Boltzmann equation approach. In the absence of
charge dephasing and for zero frequency, a finite anisotropy \sigma_{xy}
e^2/lhpf arises even for infinitesimal SOI.Comment: 6+ page
Sum rules for spin-Hall conductivity cancelation
It has been shown recently that the universal dc spin conductivity of
two-dimensional electrons with a Rashba spin-orbit interaction is canceled by
vertex corrections in a weak scattering regime. We prove that the zero bulk
spin conductivity is an intrinsic property of the free-electron Hamiltonian and
scattering is merely a tool to reveal this property in terms of the
diagrammatic technique. When Zeeman energy is neglected, the zero dc
conductivity persists in a magnetic field. Spin conductivity increases
resonantly at the cyclotron frequency and then decays towards the universal
value.Comment: 4 pages, 1 figur
Quantum-measurement backaction from a Bose-Einstein condensate coupled to a mechanical oscillator
We study theoretically the dynamics of a hybrid optomechanical system consisting of a macroscopic mechanical membrane magnetically coupled to a spinor Bose-Einstein condensate via a nanomagnet attached at the membrane center. We demonstrate that this coupling permits us to monitor indirectly the center-of-mass position of the membrane via measurements of the spin of the condensed atoms. These measurements normally induce a significant backaction on the membrane motion, which we quantify for the cases of thermal and coherent initial states of the membrane. We discuss the possibility of measuring this quantum backaction via repeated measurements. We also investigate the potential to generate nonclassical states of the membrane, in particular Schrödinger-cat states, via such repeated measurements
Stochastic heating of a molecular nanomagnet
We study the excitation dynamics of a single molecular nanomagnet by static
and pulsed magnetic fields. Based on a stability analysis of the classical
magnetization dynamics we identify analytically the fields parameters for which
the energy is stochastically pumped into the system in which case the
magnetization undergoes diffusively and irreversibly a large angle deflection.
An approximate analytical expression for the diffusion constant in terms of the
fields parameters is given and assessed by full numerical calculations.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Crossover from diffusive to non-diffusive dynamics in the two-dimensional electron gas with Rashba spin-orbit coupling
We present the calculation of the density matrix response function of the
two-dimensional electron gas with Rashba spin-orbit interaction, which is
applicable in a wide range of parameters covering the diffusive and
non-diffusive, the dirty and the clean limits. A description of the crossover
between the different regimes is thus provided as well. On the basis of the
derived microscopic expressions we study the propagating charge and
spin-polarization modes in the clean, non-diffusive regime, which is accessible
in the modern experiments.Comment: 8 pages, 6 figures, a considerable extension of the first versio
Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas
We study the coupled dynamics of spin and charge currents in a
two-dimensional electron gas in the transport diffusive regime. For systems
with inversion symmetry there are established relations between the spin Hall
effect, the anomalous Hall effect and the inverse spin Hall effect. However, in
two-dimensional electron gases of semiconductors like GaAs, inversion symmetry
is broken so that the standard arguments do not apply. We demonstrate that in
the presence of a Rashba type of spin-orbit coupling (broken structural
inversion symmetry) the anomalous Hall effect, the spin Hall and inverse spin
Hall effect are substantially different effects. Furthermore we discuss the
inverse spin Hall effect for a two-dimensional electron gas with Rashba and
Dresselhaus spin-orbit coupling; our results agree with a recent experiment.Comment: 5 page
Quantum measurement backaction from a BEC coupled to a mechanical oscillator
We study theoretically the dynamics of a a hybrid optomechanical system
consisting of a macroscopic mechanical membrane magnetically coupled to a
spinor Bose-Einstein condensate via a nanomagnet attached at the membrane
center. We demonstrate that this coupling permits us to monitor indirectly the
center-of-mass position of the membrane via measurements of the spin of the
condensed atoms. These measurements normally induce a significant backaction on
the membrane motion, which we quantify for the cases of thermal and coherent
initial states of the membrane. We discuss the possibility of measuring that
quantum backaction via repeated measurements. We also investigate the potential
to generate non-classical states of the membrane, in particular Schrodinger cat
states, via such repeated measurements.Comment: 14 pages, 4 figures. Submitted to PR
- …